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([2601:282:803:7700:4452:db16:7f2f:e7bf]) by smtp.googlemail.com with ESMTPSA id m26sm3198218qtc.83.2020.08.20.07.00.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Aug 2020 07:00:28 -0700 (PDT) Subject: Re: xdp generic default option To: Jesper Dangaard Brouer , Andrii Nakryiko Cc: Lorenzo Bianconi , Andrii Nakryiko , bpf , Networking , David Miller , Alexei Starovoitov , =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= References: <20200819092811.GA2420@lore-desk> <20200820102539.35ad8687@carbon> From: David Ahern Message-ID: Date: Thu, 20 Aug 2020 08:00:26 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200820102539.35ad8687@carbon> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/20/20 2:25 AM, Jesper Dangaard Brouer wrote: >>> diff --git a/net/core/dev.c b/net/core/dev.c >>> index a00aa737ce29..1f85880ee412 100644 >>> --- a/net/core/dev.c >>> +++ b/net/core/dev.c >>> @@ -8747,9 +8747,9 @@ static enum bpf_xdp_mode dev_xdp_mode(u32 flags) >>> { >>> if (flags & XDP_FLAGS_HW_MODE) >>> return XDP_MODE_HW; >>> - if (flags & XDP_FLAGS_DRV_MODE) >>> - return XDP_MODE_DRV; >>> - return XDP_MODE_SKB; >>> + if (flags & XDP_FLAGS_SKB_MODE) >>> + return XDP_MODE_SKB; >>> + return XDP_MODE_DRV; >>> } >>> >> >> I think the better way would be to choose XDP_MODE_DRV if ndo_bpf != >> NULL and XDP_MODE_SKB otherwise. That seems to be matching original >> behavior, no? > > Yes, but this silent fallback to XDP_MODE_SKB (generic-XDP) have > cause a lot of support issues in the past. I wish we could change it. > We already changed all the samples/bpf/ to ask for XDP_FLAGS_DRV_MODE, > so they behave this way. > I would prefer the flags check in Lorenzo's proposed patch which is an explicit opt in to the SKB mode.